We found 31 cetacean stranding events of 32 programs in the NHK Archives Collections (Kawaguchi City, Saitama Prefecture, Japan) from 1957 to 1989. One baleen whale and 12 toothed whale species (number) were identified from the events: gray whale Eschrichtius robustus (1), sperm whale Physeter macrocephalus (1), pygmy sperm whale Kogia breviceps (2), Cuvier's beaked whale Ziphius cavirostris (7), ginkgo-toothed beaked whale Mesoplodon ginkgodens (2), killer whale Orcinus orca (2), short-finned pilot whale Globicephala macrorhynchus (4), melon-headed whale Peponocephala electra (1), Risso's dolphin Grampus griseus (4), bottlenose dolphin Tursiops truncatus (1), pantropical spotted dolphin Stenella attenuata (1), northern right whale dolphin Lissodelphis borealis (1) and Pacific white-sided dolphin Lagenorhynchus obliquidens (1). One Berardius sp. was also recorded. These events occurred in 9 prefectures; Hokkaido (1), Ibaraki (3), Chiba (8), Kanagawa (14), Mie (1), Aichi (1), Hyogo (1), Nagasaki (1) and Miyazaki (1). Cuvier's beaked whale was the most frequent and all events of this species were recorded in Kanagawa prefecture. It seems the numbers in locality dose not reflect frequency distribution of the events because the data source (NHK Archives Collections) has principally collected Kanto area local news. Of 31 events, 14 were not listed in the stranding database of Whale Laboratory, Institute of Cetacean Research and National Museum of Nature and Science. Except for the stranding events, rare pygmy killer whales Feresa attenuata were recorded in dolphin fishery in Futo in Shizuoka and in Taiji in Wakayama prefectures.
In March and April 2015, a gray whale Eschrichtius robustus was sighted in two areas off central Niigata Prefecture, Sea of Japan. First, off Teradomari, Nagaoka City, adjacent to the estuary of the Ohkouzu Diversion Channel of the Shinano River in the same location where a gray whale was observed in the spring of 2014. The other sighting was in the coastal area off Tainai City, adjacent to the estuary of the Tainai River. It was identified that the Teradomari whale was the same as the Tainai whale based on the body markings. Also, the 2015 gray whale appeared was identified as the same individual as the one appeared off Teradomari in 2014. The whale was observed between 31 March and 10 April 2015 in Teradomari area, and was sighted along about 1,000m length of coast and 100m to 500m offshore from the mouth of the Ohkouzu Channel. The whale frequently appeared on the northern side of the river mouth and whale stayed for a shorter period and the area the whale was observed was smaller in 2015 than in 2014. The whale was observed in Tainai between 11 and 21 April 2015, and was sighted along a 1,200m length of the coast 100m offshore from the mouth of the Tainai River. The whale frequently appeared around outside of the breakwater structure on the southern side of the river mouth. The whale remained in areas where the bottom was sandy mud, at a depth of 3 to 7m in Teradomari and about 3m in Tainai. In both areas, the whale repeated diving and surfacing suggesting feeding behavior. The whale traveled about 70km from Teradomari to Tainai in one day. The whale stayed at central Niigata prefecture at least 22 days. This behavior of the whale suggests it was migrating to the north while feeding opportunistically. It seems the area off central Niigata was used not only for the migration route but also for feeding.